Update CHANGELOG.md

CHANGELOG.md

@@ -2,8 +2,9 @@
 
 This file needs to be updated with every significant pull request. It is used to write down release notes.
 
-## Version 0.5.7
+## Version 0.5.7 (unreleased)
 * Update data contract to align with latest schema
+* Inject JavaScript snippet on the page automatically to track client side telemetry
 
 ## Version 0.5.6
 * Expose request id to parent Rack application when using `ApplicationInsights::Rack::TrackRequest` middleware through `env['ApplicationInsights.request.id']`.